Valve assembly

ABSTRACT

A valve assembly includes a housing having an inlet and an outlet spaced from each other, a first chamber defining the inlet, a second chamber defining the outlet, and a valve seat disposed between the first and second chambers, wherein fluid communicates between the first and second chambers. A valve head is disposed in the housing and moveable relative to the housing between an open position spaced from the valve seat and a closed position engaged with the valve seat. A valve stem is coupled to the valve head for moving the valve head between the open and closed positions. The valve stem is coupled to the valve head and rotatably and reciprocally movable for moving the valve head between the open and closed positions. A retainer plate is coupled to the valve head and a valve seal is disposed between the valve head and the retainer plate. The valve head includes an integrally formed rivet that secures the retainer plate to the valve head, thereby retaining the valve seal to the valve head.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is continuation application of and claimspriority to and all benefits of U.S. patent application Ser. No.14/085,417, filed on Nov. 20, 2013, which is a divisional application ofand claims priority to and all benefits of U.S. patent application Ser.No. 12/570,763, filed on Sep. 30, 2009, which claims priority to and allthe benefits of U.S. Provisional Patent Application No. 61/101,804 filedon Oct. 1, 2008, and U.S. Provisional Patent Application No. 61/166,088filed on Apr. 2, 2009, the entire contents of which are expresslyincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve assembly, and morespecifically, a valve assembly for controlling pressures on opposingsides of the valve assembly prior to opening the valve assembly.

2. Description of the Related Art

Valve assemblies are used for regulating flow in a fluid pipelinesystem. These valve assemblies comprise a housing having a firstchamber, a second chamber, and a valve seat disposed between the firstand second chambers. A valve head is disposed in the housing and ismoveable relative to the housing between an open position spaced fromthe valve seat and a closed position engaged with the valve seat.

Valve assemblies are commonly used in a fluid pipeline system having abidirectional flow. When the valve head is in the closed position, thefluid can exert a pressure against a front portion and/or a back portionof the valve head to create a pressure differential between the frontand back portions. In one instance, when a pressure exerted on the backportion is greater than that on the front portion, the pressure on theback portion presses the valve head toward the closed position andimpedes the movement of the valve head to the open position.Additionally, the pressure on the back portion may become great enoughto cause damage to one or more elements of valve assembly and/or thefluid pipeline system. It would be desirable to have a valve capable ofequalizing the pressure between the front and back portions of the valvehead or otherwise relieving pressure build-up at the valve head.

In addition, valve assemblies of the prior art have internal componentsor structure that cause flow restrictions that interfere with the fluidflow. This interference can produce energy loss as fluid flows from aninlet to outlet of the valve assembly thereby decreasing fluid flowperformance. It would be desirable to reduce flow restrictions toincrease the flow through the valve assembly.

SUMMARY OF THE INVENTION AND ADVANTAGES

A valve assembly comprises a housing having a first chamber, a secondchamber, and a valve seat disposed between the first and secondchambers. A valve head is disposed in the housing and is moveablerelative to the housing between an open position spaced from the valveseat and a closed position engaged with the valve seat. The valve headdefines a bore therethrough along an axis. A valve stem is coupled tothe valve head for moving the valve head between the open and closedpositions. The valve stem is disposed in the bore and is moveablerelative to the valve head from a sealed position preventing fluidcommunication through the bore to an unsealed position allowing fluidcommunication through the bore for relieving pressure differencesbetween the first chamber and the second chamber when the valve head isin the closed position. An intermediate member is separate from andcoupled to the valve seat and the valve head in the bore. Theintermediate member is axially fixed to one of the valve stem and thevalve head. The other of the valve stem and the valve head defines atravel space with the intermediate member retained in the travel spacebetween the valve stem and the valve head. The travel space is sizedlarger than the intermediate member along the axis for allowingselective movement of the valve stem relative to the valve head betweenthe sealed and unsealed positions.

The valve assembly advantageously allows for the pressure between thefirst and second chambers to approach equilibrium before the valve headis moved to the open position. This is beneficial when pressure in thesecond chamber is greater than that in the first chamber such that thepressure in the second chamber urges the valve head toward the closedposition. The valve stem can be moved to the unsealed position to allowthe pressures between the first and second chambers to equilibrate priorto moving the valve head to the open position. Because the pressuresbetween the first and second chambers are equilibrated, the forcerequired to move the valve head from the closed position to the openposition is reduced.

The present invention also includes a valve assembly comprising a firstchamber, a second chamber, and a valve seat disposed between the firstand second chambers. A valve head is disposed in the housing and ismoveable relative to the housing between an open position spaced fromthe valve seat and a closed position engaging the valve seat. A valvestem is coupled to the valve head and the housing for moving the valvehead relative to the housing between the open and closed positions. Thevalve head defines a bore extending through the valve head from thefirst chamber to the second chamber when the valve head is in the closedposition. A check valve is disposed in the bore and is configured tomove between a sealed position preventing flow through the bore when apressure difference between the second chamber and the first chamber isbelow a set value and an unsealed position allowing flow through thebore when the pressure difference is greater than the set value forrelieving the pressure difference toward the set value. The valve stemextends into the bore and is engaged with the valve head in the borewith a space defined between the valve stem and the valve head in thebore for allowing flow through the bore between the valve stem and thevalve head when the check valve is in the unsealed position.

The check valve advantageously relieves the pressure difference betweenthe second and first chambers. This pressure relief prevents damage tocomponents of the valve assembly and the system to which the valveassembly is connected. This check valve is also beneficial when thepressure in the second chamber urges the valve head toward the closedposition. The check valve relieves the pressure difference such that theforce required to move the valve head from the open position to theclosed position is reduced.

The present invention also includes a valve assembly comprising ahousing defining a chamber having an inlet and an outlet spaced fromeach other along a first axis. The inlet has an inlet diameter and theoutlet has an outlet diameter greater than or equal to the inletdiameter. A valve stem is moveably engaged with the housing and extendsalong a second axis into the chamber. A valve head is disposed in andmoveable relative to the housing between an open position and a closedposition. The valve head defines a bore extending therethrough along thesecond axis with the valve stem coupled to the valve head in the borefor moving the valve head along the second axis between the open andclosed positions. The housing includes a valve seat disposed in thechamber between the inlet and the outlet with the valve seat extendingperpendicular to the second axis. The valve head engages the valve seatin the closed position and is spaced from the valve seat in the openposition. The second axis extends at an acute angle relative to thefirst axis and the housing defines a pocket extending along the secondaxis for receiving the valve head in the open position to reduce flowrestrictions between the inlet and the outlet.

Such a configuration reduces flow restrictions to increase the flowthrough the valve assembly. Specifically, outlet diameter being greaterthan or equal to the inlet diameter and the valve head being recessedinto the pocket reduces flow restrictions between the inlet and theoutlet. The valve seat being perpendicular to the second axis and thesecond axis extending at an acute angle relative to the first axis alsoreduces flow restrictions. This configuration ensures that the fluiddoes not pass through any space in which the cross-sectional area,normal to the flow, is less than the cross-sectional area of the inletand outlet, which advantageously increases the flow through the valveassembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated,as the same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is side view of a valve assembly;

FIG. 2 is a partially exploded view of the valve assembly;

FIG. 3 is a cross-sectional view of a first embodiment of the valveassembly including a valve head in a closed position;

FIG. 4 is a cross-sectional view of the first embodiment of the valveassembly with the valve head in an open position;

FIG. 5 is a cross-sectional view of the first embodiment with an rivetretaining a seal on the valve head;

FIG. 6 is a partial cross-sectional view of a second embodiment of thevalve assembly with the valve head in an open position;

FIG. 7A is a partial cross-sectional view of the second embodiment withthe valve head in the closed position and a valve stem in an unsealedposition;

FIG. 7B is a partial cross-sectional view of the second embodiment withthe valve head in the closed position and the valve stem in the sealedposition;

FIG. 8A is a magnified view of a portion of FIG. 7A;

FIG. 8B is a magnified view of a portion of FIG. 7B;

FIG. 9 is a partial cross-sectional view of a third embodiment of thevalve assembly with the valve head in the open position;

FIG. 10A is a partial cross-sectional view of the third embodiment withthe valve head in the closed position and a check valve in a sealedposition;

FIG. 10B is a partial cross-sectional view of the third embodiment withthe valve head in the closed position and the check valve in an unsealedposition; and

FIG. 11 is an exploded view of the valve head and check valve of thethird embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals indicate like orcorresponding parts throughout the several views, a valve assembly isshown generally at 20. The valve assembly 20 is of the type referred toin industry as a globe valve. As shown in FIG. 1, the valve assembly 20is typically coupled to pipes 22 of a fluid pipe system (not shown) forproviding fluid communication between the pipes 22. The fluid pipesystem can, for example, handle propane, compressed nitrogen, anhydrousammonia, petrochemicals, or other types of chemicals. The valve assembly20 can be used in, for example, bobtail, transport, and bulk plantapplications. The pipes 22 to which the valve assembly is coupled canbe, for example, 1¼″ or larger diameter.

FIG. 2 depicts a partially exploded view of the valve assembly 20. Afirst embodiment of the valve assembly 20 is shown in FIGS. 3-5; asecond embodiment of the valve assembly 20 is shown in FIGS. 6-8; and athird embodiment of the valve assembly 20 is shown in FIGS. 9-11. Commonfeatures among the three embodiments are identified with commonnumerals. The valve assemblies 20 shown in FIGS. 1-11 can be referred toin industry as globe valves; however, it is to be appreciated that thevalve assembly could also be an angle valve that changes the directionof the flow, e.g., by 90°. It is also to be appreciated that selectedtolerances shown in FIGS. 1-11 are exaggerated for illustrative purposesonly.

Referring to FIGS. 3, 6, and 9, the valve assembly 20 includes a housing24. The housing 24 defines a chamber having an inlet 26 and an outlet28. More specifically, the chamber is divided into a first chamber 30and a second chamber 32 with the first chamber 30 defining the inlet 26and the second chamber 32 defining the outlet 28. The valve assembly 20is coupled to the pipes 22 at the inlet 26 and the outlet 28. A valveseat 34 is disposed between the first 30 and second 32 chambers.

The valve assembly 20 includes a valve head 36 disposed in the housing24 and a valve stem 38 coupled to the valve head 36. The valve head 36is moveable relative to the housing 24 between an open position and aclosed position. The valve stem 38 extends along a stem axis S and thevalve stem 38 is moveably coupled to the housing 24 for moving the valvehead 36 along the stem axis S between the open and closed positions, asset forth further below. As shown in FIGS. 4-6 and 9, when the valvehead 36 is in the open position the valve head 36 is spaced from thevalve seat 34 such that the first 30 and second 32 chambers are in fluidcommunication with each other. As shown in FIGS. 3, 7A-B, and 10A-B,when the valve head 36 is in the closed position, the valve head 36 isengaged with the valve seat 34 to prevent fluid communication betweenthe first 30 and second 32 chambers. The valve stem 38 and the valvehead 36 are typically formed of metal such as stainless steel.

The inlet 26 and the outlet 28 are both generally circular in shape andare spaced from each other along a pipe axis P. Each of the inlet 26 andoutlet 28 are adapted for coupling to the pipes 22 for fluidcommunication in the fluid pipe system, e.g., via threaded fitting,press fit, etc. The diameter of the outlet 28 is greater than or equalto the inlet 26 to reduce restrictions of flow from the inlet 26 to theoutlet 28. Typically, the diameters of the inlet 26 and the outlet 28are the same.

As shown in FIGS. 3-6 and 9, the valve seat 34 is disposed centrallyabout the stem axis S between the first chamber 30 and the secondchamber 32. The valve seat 34 defines an opening 40 between the first 30and second 32 chambers. The opening 40 is defined along both the stemaxis S and the pipe axis P. In the closed position, the valve head 36 isseated on and sealed to the valve seat 34 to prevent flow through theopening 40. In the open position, the valve head 36 is spaced from thevalve seat 34 to allow flow through the valve seat 34. The valve seat 34is generally circular in shape, although other suitable shapes may beused such that the valve head 36 can seat against and seal to the valveseat 34.

The opening 40 of the valve seat 34 has a diameter to so as to minimizerestriction of flow through the housing 24. Preferably, the opening 40has a diameter that is at least 75% of the diameter of the inlet 26 andoutlet 28. More preferably, the opening 40 has a diameter that is atleast 95% of the diameter of the inlet 26 and outlet 28. Mostpreferably, the opening 40 has the same or larger diameter than thediameter of the inlet 26 and outlet 28 to maximize flow. The housing 24is constructed so that the fluid does not pass through any space inwhich the cross-sectional area, normal to the flow, is less than thecross-sectional area of the inlet 26 and outlet 28.

The pipe axis P intersects the stem axis S and is positioned at an acuteangle α from the stem axis S. The acute angle α can be from about 10degrees to about 70 degrees, more preferably from about 20 degrees toabout 50 degrees, and most preferably from about 30 degrees to about 40degrees. In one configuration, the acute angle α is about 35 degrees.The acute angle α is preferably optimized to maximize the flow rate offluid through the valve assembly 20 by reducing the twists and turns andother flow restrictions that may otherwise impede flow through the valveassembly 20 between the inlet 26 and outlet 28.

With reference to FIG. 2, the housing 24 includes a housing body 42 anda bonnet 44 attached to the housing body 42. The housing body 42includes a flange 46. A plurality of bolt fasteners 48 couples a lowerflange 50 of the bonnet 44 to the flange 46 of the housing body 42. Itis to be appreciated that any suitable fasteners may be used. A bonnetgasket 52 is disposed between the flange 46 of the housing body 42 andthe lower flange 50 of the bonnet 44 to seal between the housing body 42and the bonnet 44. The housing body 42 and the bonnet 44 are typicallyformed of metal such as ductile iron with a powder coat finish.

As shown in FIGS. 3-6 and 9, the valve stem 38 is threadedly coupled tothe bonnet 44 of the housing 24 such that rotation of the valve stem 38relative to the housing 24 moves the valve stem 38 relative to thehousing 24 along the stem axis S. Specifically, the bonnet 44 defines athroughbore 54. The valve stem 38 is disposed in the throughbore 54 andis moveably coupled to the throughbore 54. More specifically, thethroughbore 54 and the valve stem 38 are threadedly engaged.

A hand wheel 56 is coupled to the valve stem 38 to rotate the valve stem38 and move the valve head 36 between the open position and the closedposition. More specifically, the hand wheel 56 is typically rotatedclockwise to move the valve head 36 to the closed position and the handwheel 56 is rotated counterclockwise to move the valve head 36 to theopen position.

A bushing 58 is retained to the upper end of the bonnet 44 by, forexample, threaded engagement or press fit engagement. The valve stem 38extends through the bushing 58. The valve stem 38 is sealed to thebushing 58.

As best shown in FIGS. 3-5, typically, for example, one or more bushingseals 60 seal between the valve stem 38 and the bushing 58 to preventthe escape of fluid therebetween. The bushing seals 60 are generallyannular u-shaped cups, however, any other suitable configuration may beused without departing from the nature of the present invention.

A seal expander 62 is disposed between the bushing 58 and the valve stem38. An expander spring 64 is disposed in the throughbore 54 and biasesthe seal expander 62 toward the upper end of the bonnet 44, therebybiasing the bushing seals 60 toward the upper end of the bonnet 44. Anend of the seal expander 62 is generally tapered to press against thebushing seals 60 due to the bias of the expander spring 64 such that theseal expander spreads the bushing seals 60 into simultaneous contactwith the bushing 58 and the valve stem 38. The bushing seals 60 arestacked so that each bushing 58 seal forces the adjacent bushing 58 sealto spread and contact the bushing 58 and the valve stem 38.

The valve head 36 includes a back portion 66 having a first diameter anda front portion 68, having a second diameter larger than the firstdiameter. As shown in FIGS. 3 and 4, a rear seal 70 can be disposed on arear surface of the back portion 66 to prevent fluid flow through thethroughbore 54 of the bonnet 44. The lower flange 50 of the bonnet 44has a sealing surface 72 for sealing against the valve head 36 when thevalve head 36 is in the open position. When the valve head 36 is in theopen position, the rear seal 70 abuts and seals against the sealingsurface 72 to prevent fluid from flowing into the throughbore 54. Therear seal 70 may be formed of a suitable sealing material such asnitrile, PTFE (polytetrafluoroethylene), or Viton® and can be attachedto the back portion by any suitable adhesive, being press fit in achannel, etc.

As shown in FIGS. 3-6 and 9, the bonnet 44 defines a rear pocket 75.When moved to the open position, the valve head 36 is seated within therear pocket 75 and is recessed away from the flow path of fluid throughthe housing body 42 to reduce flow restrictions. Recall that the fluidpreferably does not pass through any space in which the cross-sectionalarea, normal to the flow, is less than the cross-sectional area of theinlet 26 and outlet 28. The movement of the valve head 36 into the rearpocket 75 in the open position aids in accomplishing such aconfiguration by further recessing the valve head 36 out of the flowpath along the pipe axis P.

A valve seal 74 can be disposed in an annular recess 77 (see FIG. 11)defined in the front portion 68 of the valve head 36 to seal against thevalve seat 34 when the valve head 36 is in the closed position. When thevalve head 36 is in the closed position, the valve seal 74 abuts thevalve seat 34 to prevent fluid flow from the first chamber 30 into thesecond chamber 32. The valve seal 74 may be formed of a suitable sealingmaterial such as, for example, nitrile, Teflon®, or Viton®.

A retainer plate 76 is coupled to the valve head 36 to retain the valveseal 74 in position. For example, as shown in FIG. 4, a threadedfastener 78 extends through the retainer plate 76 into the valve head 36to secure the valve seal 74 to the valve head 36. Alternatively, asshown in FIG. 5, the valve head 36 includes an integrally formed rivet80 that secures the retainer plate 76 to the valve head 36, therebyretaining the valve seal 74. In other words, during manufacturing therivet 80 is simply a cylindrical shaped protrusion (see FIG. 11) that isflattened at its distal end once the retainer plate 76 is positionedover the rivet 80 to form an enlarged head 128, i.e., the rivet 80includes a post 126 extending from the front portion 68 of the valvehead 36 and the enlarged head 128 is spaced from the front portion 68,as shown in FIGS. 9-10B. The valve seal 74 includes a hole 130 thatreceives the post 126 between the enlarged head 128 and the frontportion 68, as shown in FIGS. 9-11. For example, the rivet 80 can beformed by using an orbital forming process such that the integrallyformed rivet cooperates with the retainer plate 76 to secure theretainer plate 76. It is to be appreciated that the term orbital formingrefers to a technique for deforming a material to a desired shape.Additionally, it is to be appreciated that the retainer plate 76 may besecured to the valve head 36 using other methods known to one skilled inthe art without deviating from the nature of the present invention.

As shown in FIGS. 3-10B, the valve head 36 defines a bore 82 thatreceives the valve stem 38 with the valve stem 38 coupled to the valvehead 36 in the bore 82. Specifically, the valve stem 38 extends into thebore 82 and intermediate members 84 for example ball bearings, aredisposed between the valve stem 38 and the valve head 36 in the bore 82.The intermediate members 84 are separate from and coupled to the valvehead 36 and the valve stem 38, i.e., the intermediate members 84 areformed separately from the valve head 36 and the valve stem 38 and areintroduced between the valve head 36 and the valve stem 38 as separateunits. The intermediate members 84 engage the valve stem 38 and thevalve head 36 in the bore 82 to retain the valve head 36 in the bore 82.

The intermediate members 84 roll relative to the valve stem 38 and/orthe valve head 36 such that the valve head 36 can typically swivel 360°about the valve stem 38. When the valve head 36 contacts the valve seat34 as the valve stem 38 is rotated toward the closed position, the valvehead 36 stops rotating and the valve stem 38 is further tightened towardthe closed position to ensure proper sealing between the valve head 36and the valve seat 34. This configuration eliminates scouring of thevalve seat 34 by the valve head 36 when the valve head 36 is moved tothe closed position thereby increasing the reliability and durability ofthe valve assembly 20.

The intermediate members 84 are typically spherical; however, it is tobe appreciated that the intermediate members 84 can be any shape suchthat the intermediate members 84 retain the valve head 36 and the valvestem 38 together in a swiveling configuration. The intermediate members84 are typically formed of metal; however, it is to be appreciated thatthe intermediate members 84 can be formed of any type of rigid materialthat maintains shape during swiveling of the valve head 36 relative tothe valve stem 38.

The valve head 36 defines an aperture 86, as shown in FIGS. 3 and 4, forintroduction of the intermediate members 84 to between the valve head 36and the valve stem 38. The aperture 86 is sized to receive theintermediate members 84. A fastener, such as a set screw 88, retains theintermediate members 84 between the valve head 36 and the valve stem 38.With the set screw 88 removed from the aperture 86, the intermediatemembers 84 are introduced between the valve head 36 and the valve stem38 through the aperture 86. The set screw 88 is subsequently insertedinto the aperture 86. The set screw 88 is typically threadedly engagedwith the valve head 36 in the aperture 86.

In the first embodiment, as shown in FIGS. 3-5, the valve stem 38 andthe valve head 36 define corresponding races 90. The corresponding races90 have a shape and size corresponding to the intermediate members 84.The intermediate members 84 are retained between the valve stem 38 andthe valve head 36 in the corresponding races 90 for engaging the valvestem 38 to the valve head 36. Typically, the corresponding races 90 areeach continuous around the circumference of the bore 82; however, it isto be appreciated that one of the corresponding races 90 can bediscontinuous, i.e., a plurality of discontinuous races spaced from eachother about the circumference of the bore.

The intermediate members 84 in the corresponding races 90 retain thevalve head 36 in position along the stem axis S relative to the valvestem 38. The intermediate members 84 roll along the corresponding races90 such that the valve head 36 swivels about the valve stem 38. Thisconfiguration with the valve stem 38 extending into the bore 82 andengaging the valve head 36 in the bore 82 allows for the valve head 36to be recessed further into the rear pocket 75. This compactconstruction advantageously decreases the restriction of flow throughthe housing body 42 thereby increasing the flow through the housing body42.

The second embodiment is described in the following paragraphs. In thesecond embodiment, as shown in FIGS. 6-7B, the bore 82 extends along thestem axis S through the valve head 36 such that, when the valve head 36is in the closed position, the bore 82 extends from the first chamber 30to the second chamber 32.

The valve stem 38 selectively allows fluid communication between thefirst 30 and second 32 chambers through the bore 82 to relieve pressuredifferences between the second 32 and first chambers. Specifically, thevalve stem 38 is disposed in the bore 82 and is moveable along the stemaxis S relative to the valve head 36 from a sealed position to anunsealed position. In the sealed position, as shown in FIGS. 7B and 8B,the valve stem 38 seals to the valve head 36 and blocks the bore 82 toprevent fluid communication through the bore 82. When the valve stem 38is in the unsealed position, as shown in FIGS. 7A and 8A, the bore 82 isopen to allow fluid communication through the bore 82, i.e., the first30 and second 32 chamber 32 are in fluid communication with each otherthrough the bore 82. A space 92 is defined between the valve head 36 andthe valve stem 38 to allow fluid communication in the unsealed position.

With reference to FIGS. 6-8B, the valve head 36 defines a ledge 94 inthe bore 82. A bore seal 98 is disposed in the bore 82 between the ledge94 and the valve stem 38. As set forth further below, an end 96 of thevalve stem 38 contacts the bore seal 98 and seals against the bore seal98 when the valve stem 38 is in the sealed position and is spaced fromthe bore seal 98 when the valve stem 38 is in the unsealed position. Thebore seal 98 is formed of a suitable sealing material such as, forexample, nitrile, Teflon®, Viton®, or the like. The end 96 of the valvestem 38 has a chamfered configuration for cooperating with the bore seal98.

The intermediate members 84 are fixed along the stem axis S relative toone of the valve stem 38 and the valve head 36 with the other of thevalve stem 38 and the valve head 36 defining a travel space 100. Theintermediate members 84 are retained in the travel space 100 between thevalve stem 38 and the valve head 36. The travel space 100 typically iscontinuous about the circumference of the valve stem 38, i.e., anelongated groove. Alternatively, the travel space 100 can bediscontinuous, i.e., the valve stem 38 can define a plurality of travelspaces spaced from each other about the circumference of the valve stem38.

In the embodiment shown, the intermediate members 84 are fixed relativeto the valve head 36 and the valve stem 38 defines the travel space 100.The travel space 100 is spaced from the end 96 of the valve stem 38. Thetravel space 100 extends circumferentially about the valve stem 38.

The valve head 36 defines a depression 102 with the intermediate members84 fixed along the stem axis S in the depression 102. The depression 102can be, for example, an opposing race 104 opposing the travel space 100.However, it is to be appreciated that the depression 102 can be any sortof depression capable of fixing the intermediate members 84 along thestem axis S relative to the travel space 100.

Typically, the diameter of the intermediate members 84 generallyapproximates the size of the opposing race 104 such that theintermediate members 84 are fixed along the stem axis S relative to theopposing race 104. However; it is to be appreciated that the opposingrace 104 may be slightly larger than the diameter of the intermediatemembers 84 as long as the width of the travel space 100 along the stemaxis S is greater than the width of the opposing race 104 along the stemaxis S such that the intermediate members 84 are fixed relative to theopposing race 104 as the intermediate members 84 move along the travelspace 100, as set forth further below.

The travel space 100 is longer along the stem axis S than the opposingrace 104. Preferably, the width of the travel space 100 along the stemaxis S is at least 1% greater, more preferably at least 10% greater thanthe width of the opposing race 104 along the stem axis S. For example,the width of the travel space 100 along the stem axis S is 0.08 incheslarger than the width of the opposing race 104 along the stem axis S.

The travel space 100 is sized larger than the intermediate members 84along the stem axis S for allowing selective movement of the valve stem38 between the sealed and unsealed positions. In other words, theintermediate members 84 move relative to the travel space 100 along thestem axis S when the valve stem 38 is moved along the stem axis Sbetween the sealed and unsealed positions.

Specifically, a first wall 106 and a second wall 108 are disposed alongthe travel space 100. The first 106 and second 108 walls are spaced fromeach other along the stem axis S and oppose each other about the travelspace 100. The first wall 106 engages the intermediate members 84 whenthe end 96 contacts the bore seal 98 for preventing excessivecompression of the bore seal 98 by the end 96. The second wall 108engages the intermediate members 84 when the valve stem 38 moves towardthe unsealed position for moving the valve head 36 to the open position.The intermediate members 84 are spaced from the second wall 108 when thevalve stem 38 is in the sealed position and is spaced from the firstwall 106 when the valve stem 38 is in the unsealed position. Typically,the first 106 and second 108 walls correspond in shape to theintermediate members 84.

The valve assembly 20 of the second embodiment operates as follows.Rotation of the valve stem 38 relative to the housing 24 moves the valvestem 38 between the sealed and unsealed positions and moves the valvehead 36 between the open and closed positions. When the valve head 36 isin the closed position, the first wall 106 engages the intermediatemembers 84 such that the valve stem 38 is in the sealed position withthe bore seal 98 disposed between and sealing to the end 96 of the valvestem 38 and the ledge 94 of valve head 36, as shown in FIGS. 7B and 8B.

To move the valve head 36 to the open position, the hand wheel 56 isrotated counter-clockwise thereby traversing the valve stem 38 back upthrough the bonnet 44. Because the travel space 100 is larger than theintermediate members 84 along the stem axis S, the valve stem 38 movesfrom the sealed position to the unsealed position, i.e., the end 96 ofthe valve stem 38 separates from the bore seal 98, before the secondwall 108 engages the intermediate members 84. As such, the end 96 of thevalve stem 38 separates from the bore seal 98 before the valve head 36is moved away from the valve seat 34, as shown in FIGS. 7A and 8A. As aresult, a pressure difference that may exist between the second chamber32 and the first chamber 30 equalizes as the valve stem 38 separatesfrom the bore seal 98 before the valve head 36 is moved away from thevalve seat 34. Arrows in FIGS. 7A and 8A illustrate the flow of fluidfrom the second chamber 32 to the first chamber 30 to reduce thepressure differential therebetween. Typically the bore seal 98 isuncompressed in less than one full rotation of the hand wheel 56. Onebenefit of reducing or eliminating the pressure differential between thesecond 32 and first 30 chambers is that a force required to rotate thehand wheel 56 is reduced since the pressures in the second 32 and first30 chambers approach one another or equalize. This is particularlybeneficial when the pressure of the second chamber 32 is substantiallygreater than the pressure of the first chamber 30.

As the valve stem 38 is further rotated counter-clockwise, the valvestem 38 continues to move along the stem axis S relative to the valvehead 36 until the intermediate members 84 engage the second wall 108.Once the intermediate members 84 engage the second wall 108, furthercounter-clockwise rotation of the valve stem 38 results in movement ofthe valve head 36 from the closed position toward the open position,i.e., the valve head 36 separates from the valve seat 34. The valve stem38 is rotated counter-clockwise further to move the valve head 36 to theopen position recessed in the rear pocket 75 of the bonnet 44, as shownin FIG. 6.

To move the valve head 36 back to the closed position, the hand wheel 56is rotated clockwise thereby traversing the valve stem 38 and the valvehead 36 toward the valve seat 34. As the valve head 36 contacts thevalve seat 34, the valve head 36 ceases to rotate and the hand wheel 56is rotated clockwise further to tightly seal the valve head 36 againstthe valve seat 34 in the closed position. In the closes position, theintermediate members 84 engage the first wall 106. As set forth above,the distance between the end 96 of the valve stem 38 and the first wall106 is sized such that the end 96 properly seals against the bore seal98 without damaging the bore seal 98 by overcompression.

The third embodiment is described in the following paragraphs. In thethird embodiment, as shown in FIGS. 9-10B, the bore 82 extends throughthe valve head 36 from the inlet 26 to the outlet 28 when the valve head36 is in the closed position. An integrated back check valve,hereinafter referred to as check valve 110, is disposed in the bore 82and is configured to move between a sealed position and an unsealedposition. In the sealed position, as shown in FIG. 10A, the check valve110 prevents flow through the bore 82 when a pressure difference betweenthe inlet 26 and the outlet 28 is below a set value. In the unsealedposition, as shown in 10B, the check valve 110 allows flow through thebore 82 when the pressure difference is greater than the set value forrelieving the pressure difference. A space 112 is defined between thevalve stem 38 and the valve head 36 and also between the intermediatemembers 84 in the bore 82 for allowing flow through the bore 82 betweenthe valve stem 38 and the valve head 36 when the check valve 110 is inthe unsealed position. This configuration with the valve stem 38engaging the valve head 36 in the bore and with the check valve 110disposed in the bore is an advantageously compact construction therebyreducing flow restriction when the valve head 36 is in the openposition.

The intermediate members 84 are disposed in the bore 82 between thevalve stem 38 and the valve head 36 with the intermediate members 84fixed relative to the valve stem 38 and the valve head 36 along the stemaxis S. The valve stem 38 and the valve head 36 define correspondingraces 114 in the bore 82 with the intermediate members 84 retained inthe corresponding races 114 between the valve stem 38 and the valve head36 such that the valve head 36 swivels relative to the valve stem 38.The corresponding races 114 extend circumferentially about the valvestem 38. A diameter of each of the intermediate members 84 generallyapproximates the diameter defined by the corresponding races 114 butstill allowing each of the intermediate members 84 to freely traverse inthe corresponding races 114.

An exploded view of the check valve 110 is shown in FIG. 11. The checkvalve 110 includes a plug 116 sealing to the valve head 36 in the bore82 in the sealed position, as shown in FIG. 10A, and spaced from thevalve head 36 in the unsealed position, as shown in FIG. 10B. The checkvalve 110 includes a plug holder 118 defining a cavity for receiving theplug 116. A spring 120 is coupled to the plug 116 by abutting the plugholder 118 to urge the plug 116 toward the sealed position, as set forthfurther below. The plug 116 is preferably formed of a suitable sealingmaterial such as nitrile, Teflon®, Viton®, or the like.

The bore 82 changes diameter to define a check valve seat 122. The checkvalve 110 is disposed in the bore 82 adjacent the check valve seat 122.A circumference of the plug holder 118 has a polygon configuration andthe bore has a cylindrical shape for defining flow paths between theplug holder 118 and the valve head 36 for providing fluid communicationthrough the bore 82 when the check valve 110 is in the unsealedposition.

A spring retainer 124 is disposed in the bore 82 with a spring 120disposed between the spring retainer 124 and the plug holder 118. Thespring 120 is typically a coil spring 120 formed of metal such asstainless steel. The spring retainer 124 engages the valve head 36 inthe bore 82 such that the spring retainer 124 retains the spring 120 inthe bore 82 and supports the spring 120. The spring retainer 124 may beformed of metal or non-metal materials. The spring retainer 124 can be,for example, press fit, welded or otherwise fixed to the valve head 36.

The check valve 110 operates as follows. When the check valve 110 is inthe sealed position and the pressure difference between the secondchamber 32 and the first chamber 30 exceeds the set value, the pressureon the plug 116 overcomes opposing force providing by the spring 120 incombination with any pressure in the first chamber 30 such that thespring 120 compresses and the plug 116 moves away from the check valveseat 122 to allow communication between the first 30 and second 32chambers through the bore 82. As a result, the pressures of the first 30and second 32 chambers begin to equilibrate until the pressuredifference reaches the set value. At that time, the spring 120 overcomesthe pressure on the plug 116 to bias the relief plug 116 back againstthe check valve seat 122. Preferably, the set value is greater than 75pounds per square inch (psi), more preferably between 75 and 100 psi. Itis to be appreciated that the “set value” is a predetermined value thatbe changed by changing components of the check valve 110 such as, forexample, altering the spring constant of the spring 120.

Such a configuration advantageously alleviates pressure in a downstreamfluid pipe 22 that has a closed downstream valve (not shown). Forinstance, the pipe 22 may have a main relief valve set to open at arelief pressure, e.g., 400 psi or greater. When the valve assembly 20 isclosed and the downstream valve is closed, a closed spaced is definedbetween the check valve 110 and the downstream valve. If this space isheated, the fluid pressure increases. Without the check valve 110, ifthe pressure in the downstream pipe 22 increases beyond the reliefpressure, fluid in the downstream pipe is lost through the main reliefvalve to the atmosphere. The check valve 110 of the present inventioncan be incorporated into such a system to prevent such loss of fluid tothe atmosphere by relieving the excess pressure in the closed space tothe upstream pipe or container.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation.Obviously, many modifications and variations of the present inventionare possible in light of the above teachings, and the invention may bepracticed otherwise than as specifically described.

What is claimed is:
 1. A valve assembly comprising: a housing having aninlet and an outlet spaced from each other, a first chamber definingsaid inlet, a second chamber defining said outlet, and a valve seatdisposed between said first and second chambers, wherein fluidcommunicates between said first and second chambers; a valve headdisposed in said housing and moveable relative to said housing betweenan open position spaced from said valve seat and a closed positionengaged with said valve seat; a valve stem coupled to said valve headand being rotatably and reciprocally movable for moving said valve headbetween said open and closed positions; a retainer plate coupled to saidvalve head; a valve seal disposed between said valve head and saidretainer plate; and wherein said valve head includes an integrallyformed rivet that secures said retainer plate to said valve head,thereby retaining said valve seal to said valve head.
 2. The valveassembly as set forth in claim 1 wherein said rivet has an enlarged headat a distal end of said rivet.
 3. The valve assembly as set forth inclaim 2 wherein said valve head includes a front portion, said valveseal being disposed adjacent said front portion.
 4. The valve assemblyas set forth in claim 3 wherein said rivet includes a post extendingfrom said front portion of said valve head and said enlarged headextends from said post and is spaced from said front portion of saidvalve head.
 5. The valve assembly as set forth in claim 4 wherein saidretainer plate includes a hole to receive said post and said retainerplate is disposed between said enlarged head and said front portion. 6.The valve assembly as set forth in claim 1 wherein said rivet is formedby an orbital forming process such that said rivet cooperates with saidretainer plate to secure said retainer plate to said valve head.
 7. Avalve assembly comprising: a housing having a first chamber, a secondchamber, and a valve seat disposed between said first and secondchambers; a valve head disposed in said housing and moveable relative tosaid housing between an open position spaced from said valve seat and aclosed position engaged with said valve seat, said valve head having afront portion and a rear portion; a valve stem coupled to said rearportion of said valve head and being rotatably and reciprocally movablefor moving said valve head between said open and closed positions;wherein said valve head includes a post extending from said frontportion and integrally formed with the valve head; a valve sealincluding a hole receiving said post and being disposed adjacent saidfront portion; a retainer plate having a hole to receive said post andbeing disposed adjacent said valve seal; and wherein said post has anenlarged head at a distal end of said post spaced from said frontportion to secure said retainer plate to said valve head, therebyretaining said valve seal to said valve head.
 8. A method of assemblinga valve assembly, said method comprising the steps of: providing ahousing having an inlet and an outlet spaced from each other, a firstchamber defining the inlet, a second chamber defining the outlet, and avalve seat disposed between the first and second chambers, wherein fluidcommunicates between the first and second chambers; disposing a valvehead in the housing and being moveable relative to the housing betweenan open position spaced from the valve seat and a closed positionengaged with the valve seat; coupling a valve stem to the valve head andbeing rotatably and reciprocally movable for moving the valve headbetween the open and closed positions; disposing a valve seal adjacentthe valve head; disposing a retainer plate adjacent the valve seal; andforming a rivet integrally with the valve head and securing the retainerplate to the valve head, thereby retaining the valve seal to the valvehead.
 9. The method as set forth in claim 8 including the step ofextending a post of the rivet from a front portion of the valve head.10. The method as set forth in claim 9 including the step of receivingthe post in a hole of the valve seal.
 11. The method as set forth inclaim 10 including the step of receiving the post in a hole of theretainer plate.
 12. The method as set forth in claim 11 including thestep of enlarging the post at a distal end of said post to form anenlarged head.
 13. The method as set forth in claim 8 including the stepof forming the rivet by an orbital forming process such that the rivetcooperates with the retainer plate to secure the retainer plate to thevalve head.
 14. A method of assembling a valve assembly, said methodcomprising the steps of: providing a housing having an inlet and anoutlet spaced from each other, a first chamber defining the inlet, asecond chamber defining the outlet, and a valve seat disposed betweenthe first and second chambers, wherein fluid communicates between thefirst and second chambers; disposing a valve head in the housing andbeing moveable relative to the housing between an open position spacedfrom the valve seat and a closed position engaged with the valve seat,the valve head having a front portion and a rear portion; coupling avalve stem to the rear portion of the valve head and being rotatably andreciprocally movable for moving the valve head between the open andclosed positions; extending a post from a front portion of the valvehead; disposing a valve seal having a hole adjacent the front portion ofthe valve head such that the post extends through the hole of the valveseal; disposing a retainer plate having a hole adjacent the valve sealsuch that the post extends through the hole of the retainer plate; andenlarging the post at a distal end of the post to form an enlarged headby orbital forming to form a rivet integrally with the valve head andsecuring the retainer plate to the valve head, thereby retaining thevalve seal to the valve head.